Rubber solution production method and rubber solution production device

ABSTRACT

In order to both produce a high quality rubber solution that preserves the molecular structure of the rubber and improve productivity, the rubber solution is created by mixing a solvent ( 7 ) into a source material ( 6 ), stirring while applying a shear force to the source material ( 6 ), and separating the source material ( 6 ) into block ( 61 ) units that are subsequently dissolved in the solvent ( 7 ), thereby continuously performing a solvent addition process, a source material addition process, a separation process, a dissolving process, and a mixing process in a single container ( 2 ).

TECHNICAL FIELD

The present invention relates to a rubber solution production method anda rubber solution production device which dissolve rubber to a solventto produce a rubber solution.

BACKGROUND ART

The following method is adopted to produce a rubber solution from asource material which is a large piece of rubber. The source material isfragmented into small pieces, and then the small pieces of rubber aremixed with a solvent and stirred, thereby dissolving the rubber into thesolvent. In this method, the source material is fragmented into smallpieces by, for example, a guillotine-like cutting apparatus which movesup and down a cutting blade to cut the source material into a plate-likeform, or a cutting apparatus having a cutting blade disposedhorizontally to form a space between the blade and a table, the cuttingapparatus slicing the source material by advancing and retracting thesource material on the table. Further, the following apparatusesdescribed in Patent documents 1 and 2 are also adoptable.

Namely, Patent document 1 discloses a structure in which a cut screw isprovided to a discharge port of a hopper, and a sprocket for deliveringthe source material towards the discharge port is provided at the bottomof the hopper. With this structure, the source material supplied to thehopper is successively fed to the cut screw and pulverized. Further,Patent document 2 discloses a structure in which a fixed blade and arotating blade are provided inside a drum, and the source materialsupplied to the drum is successively cut by the fixed blade and therotating blade. After fragmentation using any of these apparatuses,small pieces of rubber obtained are supplied to a stirring device alongwith a solvent, mixed, and stirred to form a rubber solution.

PRIOR ART DOCUMENT Patent Document

-   [Patent document 1] Japanese Unexamined Patent Publication No.    225979/2002 (Tokukai 2002-225979)-   [Patent document 2] Japanese Unexamined Patent Publication No.    240015/1999 (Tokukaihei 11-240015)

DISCLOSURE OF THE INVENTION Technical Problem

However, when the source material is pulverized without any conditionsetting, the molecular structure of the rubber structuring the sourcematerial may be destroyed and the quality of the rubber solution maydeteriorate. Further, the method involving a device for fragmenting thesource material and another apparatus for dissolving the small pieces ofrubber requires various operations such as storing and transferring ofthe source material fragmented into small pieces, and supplying of thesame to a stirring device. This leads to an insufficient productivity.

In view of the above problems, the present invention is made, and it isan object of the present invention to provide a rubber solutionproduction method and a rubber solution production device which allowproduction of a high-quality rubber solution which preserves themolecular structure of the rubber, while improving the productivity.

Technical Solution

An aspect of the present invention is a rubber solution productionmethod, including the steps of: mixing a solvent into a source materialincluding a plurality of rubber blocks each maintaining a block-state bya predetermined holding force, the blocks being adhered to one anotherby an adhesion force smaller than the holding force; and stirring thesource material while applying thereto a shear force which is greaterthan the adhesion force but smaller than the holding force so as toseparate the source material into block units, and dissolving the blocksinto the solvent to produce a rubber solution.

With the structure, the source material is stirred while being subjectedto a shear force which is greater than the adhesion force of the blocksbut smaller than the holding force of each block. This way, whilepreventing destruction of each block by the shear force, adhesionsurfaces of the blocks are separated from each other by the shear force.As the result, the blocks are separated into block units, whilepreventing destruction of the molecular structure of the rubber blocks.Since destruction of the molecular structure of the blocks is prevented,continuing to stir the blocks and the solvent thereafter causes theblocks to dissolve into the solvent starting from their surfaces, whilepreserving the molecular structure of the rubber. As the result, ahigh-quality rubber solution is produced which preserves the molecularstructure of the rubber, and the productivity is improved because theseries of operations enables production of the rubber solution from therubber source material.

Further, the present invention may be adapted so that the sourcematerial is stirred while applying thereto the shear force, by moving aplurality of stirring blades (encompassing a projection formed insidethe container serving as a tank) at speeds relatively different fromeach other (in the same direction, one of the blade stopped, or inopposite directions to each other), the blades being disposed so that aminimum gap between the blades is greater than the average maximumflattened-dimension of the blocks and smaller than the average maximumdiameter of the blocks.

The above structure allows application of a desirable shear force to thesource material while stirring the source material, with a use of arelatively simple structure such as a mechanism of rotating the stirringblades, and through a simple operation such as adjustment of therotation speed or the like, which can be carried out even during theprocess.

Further, the present invention may be adapted so that the sourcematerial is separated into block units by stirring the source materialand the solvent, while cooling down the same.

Cooling down the source material and the solvent as described abovehinders dissolving of the rubber source material into the solvent.Therefore, separation of the blocks is prioritized. This preventsreduction of the maximum diameter and the maximum flattened-dimension ofeach block before the blocks are separated from one another. Therefore,the separation of the blocks is completed within a short period of time.

Further, the present invention may be adapted so that the sourcematerial and the solvent are stirred in such a manner as to add anascending force.

Adding the ascending force to lift up the source material when stirringthe source material and the solvent creates an active flow of the sourcematerial. This way, the shear force is efficiently applied to the entiresource material. As the result, separation of each block from oneanother is completed in a short time.

Further, the present invention may be adapted so that a stirring state(stirring speed, stirring direction, or stirring temperature) is changedaccording to a ratio of the rubber dissolved into the solvent.

Changing the stirring state according to the ratio of rubber dissolvedin the solvent accelerates the speed of dissolving the rubber in thesolvent. It is therefore possible to completely dissolve the rubber inthe solvent in a short time.

Further, the present invention may be adapted so that the stirring iscarried out under a pressure exceeding an atmospheric pressure.

This structure allows stirring of the solvent and the rubber in anenvironment where the temperature is higher than the boiling temperatureof the solvent under the atmospheric pressure. Therefore, the swellingspeed of the solvent relative to the rubber is increased, and themixability is improved by a decrease in the visibly-confirmableviscosity of the solution. As the result, the time taken for dissolvingis reduced.

Another aspect of the present invention is a rubber solution productiondevice, including: a container configured to store a solvent and asource material including a plurality of rubber blocks each maintaininga block-state by a predetermined holding force, the blocks being adheredto one another by an adhesion force smaller than the holding force; anda stirring mechanism configured to stir the source material and thesolvent, while applying, to the source material a shear force greaterthan the adhesion force but smaller than the holding force.

With the structure, the source material is stirred while being subjectedto a shear force which is greater than the adhesion force of the blocksbut smaller than the holding force of each block. This way, whilepreventing destruction of each block by the shear force, adhesionsurfaces of the blocks are separated from each other by the shear force.As the result, the blocks are separated into block units, whilepreventing destruction of the molecular structure of the rubber blocks.Since destruction of the molecular structure of the blocks is prevented,continuing to stir the blocks and the solvent thereafter causes theblocks to dissolve into the solvent starting from their surfaces, whilepreserving the molecular structure of the rubber. As the result, ahigh-quality rubber solution is produced which preserves the molecularstructure of the rubber, and the productivity is improved because theseries of operations enables production of the rubber solution from therubber source material.

Further, the present invention may be adapted so that the stirringmechanism includes: a plurality of stirring blades disposed so that aminimum gap between the blades is greater than the average maximumflattened-dimension of the blocks and smaller than the average maximumdiameter of the blocks; and a drive mechanism configured to move thestirring blades at speeds relatively different from each other. Theabove structure allows application of a desirable shear force to thesource material while stirring the source material, with a use of arelatively simple structure such as a mechanism of rotating the stirringblades, and through a simple operation such as adjustment of therotation speed or the like, which can be carried out even during theprocess.

Further, the present invention may further include a temperatureadjusting mechanism for cooling down the source material and thesolvent. Cooling down the source material and the solvent as describedabove hinders dissolving of the rubber source material into the solvent.Therefore, separation of the blocks is prioritized. This preventsreduction of the maximum diameter and the maximum flattened-dimension ofeach block before the blocks are separated from one another. Therefore,the separation of the blocks is completed within a short period of time.

Further, the present invention may be adapted so that the stirringmechanism includes an ascending stirring blade configured to add anascending force to the source material. Adding the ascending force tolift up the source material when stirring the source material and thesolvent creates an active flow of the source material. This way, theshear force is efficiently applied to the entire source material. As theresult, separation of each block from one another is completed in ashort time.

Further, the present invention may be adapted so that the container isformed so as to airtightly store the source material and the solvent;and the rubber solution production device further includes apressurizing device for pressurizing the inside of the container to apressure exceeding an atmospheric pressure.

This structure allows stirring of the solvent and the rubber in anenvironment where the temperature is higher than the boiling temperatureof the solvent under the atmospheric pressure. Therefore, the swellingspeed of the solvent relative to the rubber is increased, and themixability is improved by a decrease in the visibly-confirmableviscosity of the solution. As the result, the time taken for dissolvingis reduced.

Advantageous Effects

The present invention allows production of a high-quality rubbersolution which preserves the molecular structure of the rubber, whileimproving the productivity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory diagram showing an embodiment of a rubbersolution production method, according to the present invention.

FIG. 2 is an explanatory diagram showing an embodiment of a rubbersolution production device, according to the present invention.

FIG. 3 is an explanatory diagram of a minimum gap.

FIG. 4 is an explanatory diagram showing a process in which a block isseparated.

FIG. 5 is an explanatory diagram showing an embodiment of a rubbersolution production device, according to the present invention.

FIG. 6 is an explanatory diagram showing an embodiment of a rubbersolution production method, according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The following describes a preferable embodiment of the presentinvention, with reference to attached drawings. (Rubber SolutionProduction Method) As shown in FIG. 1, in the present embodiment of arubber solution production method, a solvent 7 is mixed into a sourcematerial 6 and stirred while applying a shear force to the sourcematerial 6 so as to separate the source material 6 into block 61 units,and then dissolve each block 61 into the solvent 7 to produce a rubbersolution. In this method, a solvent addition process, a source materialaddition process, a separation process, a dissolving process, and amixing process are successively carried out in a single container 2.Note that the above description reading “a solvent 7 is mixed into asource material 6” is not intended to limit the sequence of adding thesource material 6 and the solvent. The source material 6 and the solvent7 may be supplied at the same time, or one of them may be suppliedbefore the other.

The “source material 6” includes a plurality of rubber blocks 61 adheredto one another to form one piece of source material 6. The rubber blocks61 each maintains the block-state by a predetermined holding force.Thus, application of a shear force less than the holding force to any ofthe rubber blocks 61 will deform that rubber block 61 into a flattenedshape, but will not destroy the same, and the block-state is thereforemaintained. The blocks are adhered to one another by an adhesion forcewhich is smaller than the holding force. Thus, the source material 6achieves: the holding force of the block > the adhesion force of theblocks. Therefore, the adhesion of the blocks are cancelled, before eachblock is destroyed, by applying a shear force exceeding the adhesionforce but falling short of the holding force of each block.

The rubber structuring the blocks is not particularly limited as long asthe following relation is achieved: the holding force of each block >the adhesion force of the blocks. Specifically, examples of rubberinclude a synthetic rubber such as PIB (Polyisobutylene) rubber.Further, the lower limit value of the weight-average absolute molecularweight of the rubber is 750000 or higher, preferably 3500000 or higher,and more preferably higher 3600000 or higher. The upper limit value ofthe same is 1000000 or lower, preferably 4200000 or lower, and morepreferably 4300000. That is, the rubber has a weight-average absolutemolecular weight within nine possible ranges each of which is acombination of one of the above mentioned lower limit values and one ofthe above-mentioned upper limit values of the weight-average absolutemolecular weight.

The “solvent 7” may be any given liquid provided that the rubber isdissolved. For example, the solvent 7 may be one type of solvent such astoluene or hexane, or a mixture of different types of solvents such as amixture of toluene and hexane.

In the above production method, the source material 6 is stirred whilebeing subjected to a shear force which is greater than the adhesionforce of the blocks but smaller than the holding force of each block 61.This way, while preventing destruction of each block 61 by the shearforce, adhesion surfaces of the blocks 61 are separated from each otherby the shear force. As the result, the blocks 61 are separated intoblock 61 units, while preventing destruction of the molecular structureof the rubber blocks 61. Since destruction of the molecular structure ofthe blocks 61 is prevented, continuing to stir the blocks 61 and thesolvent 7 thereafter causes the blocks 61 to dissolve into the solvent 7starting from their surfaces, while preserving the molecular structureof the rubber. As the result, a high-quality rubber solution is producedwhich preserves the molecular structure of the rubber, and theproductivity is improved because the series of operations enablesproduction of the rubber solution from the rubber source material 6.

The shear force applied to the blocks 61 is generated by moving aplurality of stirring blades (specifically, a first stirring blade 43and a second stirring blade 53) at speeds relatively different from eachother. These stirring blades are disposed so that a minimum gaptherebetween is greater than the average maximum flattened-dimension ofthe blocks 61 but smaller than the average maximum diameter of theblocks 61. Note that, as shown in FIG. 2, the “maximumflattened-dimension” is the thickness of the block 61 relative to adirection of flattening (a direction of applying an external force), thethickness resulting from applying the external force to the block toflatten the same until immediately before the block 61 is destroyed.Further, the “maximum diameter” means the maximum outer diameter of theblock 61 when the block 61 is suspended alone in the solvent 7. The“minimum gap” is the smallest gap formed between the stirring blades(gap between the first stirring blade 43 and the second stirring blade53).

When the minimum gap between the stirring blades is set as describedabove, the blocks 61 are not destroyed even if they are in the minimumgap between the stirring blades. This is because the minimum gap isgreater than the maximum flattened-dimension. Further, when theseparation of the blocks 61 progresses and the blocks 61 are separatedinto groups of two or three blocks 61, these groups will not exit thegap without being sandwiched between the stirring blades. This isbecause the minimum gap is smaller than the maximum diameter of theblock 61. As the result, in the present embodiment, application of theshear force to the source material 6 separates each of the blocks 61from one another, without crushing each block 61.

As shown in FIG. 1, the rubber solution production method includes, atleast in the separation process, a cooling process for cooling thesource material 6 and the solvent 7 while stirring them. Note that thewording “cooling” means to cool down the temperature to a stirringtemperature. The stirring temperature is within a range of temperatureslower than the room temperature (25° C.) but higher than a temperaturethat makes each block 61 of the source material 6 deformable to anextent a desirable ellipticity is achieved. Specifically, the coolingprocess cools down the temperature to a stirring temperature within arange of −5° C. to 25° C., preferably within a range of 10° C. to 25° C.

Cooling down the source material 6 and the solvent 7 as described abovehinders dissolving of the rubber source material 6 into the solvent 7.Therefore, separation of the blocks 61 is prioritized. This preventsreduction of the maximum diameter and the maximum flattened-dimension ofeach block 61 before the blocks 61 are separated from one another.Therefore, the separation of the blocks 61 is completed within a shortperiod of time.

Further, in the rubber solution production method, the source material 6and the solvent 7 are stirred in such a manner as to add an ascendingforce. Adding the ascending force to lift up the source material whenstirring the source material 6 and the solvent 7 creates an active flowof the source material 6. This way, the shear force is efficientlyapplied to the entire source material 6. As the result, separation ofeach block 61 from one another is completed in a short time.

Further, in the rubber solution production method, a stirring state ischanged according to the ratio of rubber dissolved in the solvent 7. The“stirring state” here means various stirring factors such as a stirringspeed, a stirring direction, a timing of switching the stirringdirection, and a stirring temperature, and a combination of thesefactors. Specifically, when preparing a rubber solution whose viscosityincreases with an increase in the ratio of rubber dissolved in thesolvent 7, the stirring speed and/or the stirring temperature areincreased according to the ratio resulting in an increase in theviscosity. Changing the stirring state according to the ratio of rubberdissolved in the solvent 7 accelerates the speed of dissolving therubber in the solvent 7. It is therefore possible to completely dissolvethe rubber in the solvent in a short time.

(Rubber Solution Production Device)

As shown in FIG. 2, the above-described rubber solution productionmethod is carried out in a rubber solution production device 1. Notethat the rubber solution production method may be carried out in otherproduction devices. The rubber solution production device 1 includes acontainer 2 for storing the source material 6 and the solvent 7; anupper stirring mechanism 4 and a lower stirring mechanism 5 each servingas a stirring mechanism for stirring the source material 6 and thesolvent 7.

(Rubber Solution Production Device: Container 2)

The container 2 has a cylindrical storing body 22 whose top is opened,and a cover 21 detachably provided on top of the storing body 22, whichis capable of hermetically close the opening of the storing body 22. Thetop of the storing body 22 is opened and has: a body 221 whosetransverse section is in a circular shape; and a bottom part 222 jointedto the lower periphery of the body 221, the bottom part being curved toform a convex so that its center portion is the lowermost end of thebody 22.

In the upper portion of the storing body 22 is disposed the cover 21. Onthe cover 21 are formed various supply ports such as a solvent supplyport 21 a. Each of these supply ports are formed so as to be opened orclosed by an open-close valve. Further, the cover 21 is supported by anot-shown cover open/close mechanism. The cover open/close mechanism hasat least a function of elevating the cover 21, which is realized by ahydraulic cylinder device or the like. The cover open/close mechanismlifts up the cover 21 to open the top of the storing body 22 through anascending operation, and descends the cover 21 to hermetically close thetop of the storing body 22 through a descending operation. This way, thecontainer 2 is able to form therein an airtight storage space 23. Inthis storage space 23, the source material 6 is stirred with the solvent7 so that each of the blocks 61 are separated from one another. Afterthis, the blocks 61 are dissolved into the solvent 7 to generate arubber solution.

(Rubber Solution Production Device: Stirring Mechanism)

The container 2 is provided with the stirring mechanism. The stirringmechanism includes an upper stirring mechanism and a lower stirringmechanism 5. The upper stirring mechanism 4 is provided to the cover 21.The upper stirring mechanism 4 has a first stirring drive device 41, afirst stirring shaft 42, and a first stirring blade 43. The firststirring drive device 41 is fixed to a center portion of the top surfaceof the cover 21. The first stirring drive device 41 is structured by anAC motor or the like with a decelerating mechanism, and is structured sothat the rotating direction is switchable and that the rotation speed ischangeable to any given rotation speed by changing the frequency of thedrive power. To the first stirring drive device 41 is connected arod-shaped first stirring shaft 42. The first stirring shaft 42 has itsaxis set in the vertical direction, and rotatably and airtightlypenetrates the center of the cover 21.

The first stirring shaft 42 is disposed so that its lower end ispositioned above the storing body 22. To the lower end portion of thefirst stirring shaft 42 is provided a first stirring blade 43. Note thatFIG. 2 shows a single first stirring blade 43; however, there may bemore than one first stirring blade 43. The first stirring blade 43 has asupport member 431 and a first blade 432 fixed to the leading endportion of the support member 431. The first blade 432 is formed in aplate-like shape, with its length parallel to the vertical direction,and its width parallel to a radial direction of the storing body 22.Thus, the first blade 432, when rotating about the first stirring shaft42, stirs the source material 6 and the solvent 7 with its wall surfacewhich crosses the rotating direction.

Note that the first blade 432 may have its width crossed (slanted withrespect to) the radial direction of the storing body 22. In such a case,when the first blade 432 is rotated so that the outer circumference sideof the blade leads the inner circumference side of the same (clockwiserotation), the source material 6 or the like is stirred and flowstowards the inner circumference of the storing body 22. On the otherhand, when the first blade 432 is rotated so that the innercircumference side of the blade leads the outer circumference side ofthe same (counterclockwise rotation), the source material 6 or the likeis stirred and flows towards the outer circumference of the storing body22.

Further, the first blade 432 may have its length crossed (slanted withrespect to) the vertical direction. In this case, when the first blade432 is rotated so that the upper end side of the blade leads the lowerend side of the same (clockwise rotation), the source material 6 or thelike is stirred and flows towards the lower side of the storing body 22.On the other hand, when the first blade 432 is rotated so that the lowerend side of the blade leads the upper end side of the same(counterclockwise rotation), the source material 6 or the like isstirred and flows towards the upper side of the storing body 22.

Further, the outer end surface of the first blade 432 faces the innerwall surface of the storing body 22. The first blade 432 is spaced fromthe inner wall surface of the storing body 22, so that the first blade432 functions as a scraper for scraping the source material 6 adheringto the inner wall surface of the storing body 22.

Below the upper stirring mechanism 4 having the above-describedstructure is disposed a lower stirring mechanism 5. The lower stirringmechanism 5 is provided to the bottom part 222 of the storing body 22.The lower stirring mechanism 5 has a second stirring drive device 51, asecond stirring shaft 55, and a second stirring blade 53. The secondstirring drive device 51 is fixed to a center portion of the bottomsurface of the storing body 22. The second stirring drive device 51 isstructured by an AC motor or the like with a decelerating mechanism, andis structured so that the rotating direction is switchable and that therotation speed is changeable to any given rotation speed by changing thefrequency of the drive power. The rotation of the second stirring drivedevice 51 is controlled along with the rotation of the first stirringdrive device 41 so that the two blades rotate in the same direction orone of the two blades stops rotating or rotates in the oppositedirection to the other. This way, the first stirring blade 43 and thesecond stirring blade 53 rotate at relatively different speeds,respectively. Note that a projection part may be formed on the innersurface of the container, instead of the upper stirring mechanism 4.

To the second stirring drive device 51 is connected a rod-shaped secondstirring shaft 55. The second stirring shaft 55 has its axis set in thevertical direction, and rotatably and airtightly penetrates the centerof the bottom part 222.

The second stirring shaft 55 is disposed so that its upper end ispositioned above the level of the lower end of the blade 44. To theupper end of the second stirring shaft 55 is attached a second stirringblade 53. As shown in FIG. 3, the second stirring blade 53 has a bladesupport member 532 which is fixed to the second stirring shaft 55, andfour second blades 531 extended in four directions from the bladesupport member 532, respectively. The number of the second blades 531however is not limited to this, as long as the number is more than one.Each of the second blades 531 is formed in a plate-like shape, with itswidth parallel to the vertical direction, and its length parallel to aradial direction of the storing body 22. Thus, the second blade 531,when rotating about the second stirring shaft 55, stirs the sourcematerial 6 and the solvent 7 with its wall surface which crosses therotating direction.

Note that the second blade 531 may have its length crossed (slanted withrespect to) the radial direction of the storing body 22. In such a case,when the second blade 531 is rotated so that the outer circumferenceside of the blade leads the inner circumference side of the same(clockwise rotation), the source material 6 or the like is stirred andflows towards the inner circumference of the storing body 22. On theother hand, when the second blade 531 is rotated so that the innercircumference side of the blade leads the outer circumference side ofthe same (counterclockwise rotation), the source material 6 or the likeis stirred and flows towards the outer circumference of the storing body22.

Further, the second blade 531 may have its width crossed (slanted withrespect to) the vertical direction. In this case, when the second blade531 is rotated so that the upper end side of the blade leads the lowerend side of the same (clockwise rotation), the source material 6 or thelike is stirred and flows towards the lower side of the storing body 22.On the other hand, when the second blade 531 is rotated so that thelower end side of the blade leads the upper end side of the same(counterclockwise rotation), the source material 6 or the like isstirred and flows towards the upper side of the storing body 22.

Further, the minimum gap between the first stirring blade 43 and thesecond stirring blade 53 is greater than the average maximumflattened-dimension of the blocks 61 but smaller than the averagemaximum diameter of the blocks 61. The leading end portions of the firststirring blade 43 and the second stirring blade 53 are formed in asemi-circular shape so that the blocks 61 are not scratched by a sharpcorner.

Below the second stirring blade 53 is disposed an ascending stirringmechanism 52. The ascending stirring mechanism 52 is provided to thebottom part 222 of the storing body 22. The ascending stirring mechanism52 has an ascending stirring blade 521 which adds an ascending force tothe source material 6 and the solvent 7; and an ascending stirring shaft54 connected to the rotational axis of the ascending stirring blade 521.The ascending stirring shaft 54 is formed in a circular-ring shape, thesecond stirring shaft 55 airtightly penetrates therethrough. To thelower end of the ascending stirring shaft 54 is applied a rotation driveforce through a transmission mechanism such as Continuously VariableTransmission (CVT), in the second stirring drive device 51. Theascending stirring blade 521 may be connected to the second stirringshaft 55 for rotating the second stirring blade 53 so as to rotate withthe second stirring blade 53.

(Rubber Solution Production Device: Temperature Adjusting Mechanism 3)

The container 2 with the above-described structure further includes atemperature adjusting mechanism 3 for cooling the source material 6 andthe solvent 7. The temperature adjusting mechanism 3 has a storing bodyjacket 31 which covers the outer wall surface of the storing body 22.The storing body jacket 31 is structured so that a coolant such ascooling water and a heating medium such as oil or water vapor can besupplied. This way, the temperature adjusting mechanism 3 is able toadjust the temperatures of the source material 6 and the solvent 7 todesirable temperatures, from low temperatures to high temperatures.

(Operation of Rubber Solution Production Device)

The following describes an operation of the rubber solution productiondevice 1 having the above described structure. First, as shown in FIG.1, the cover 21 is lifted and separated from the storing body 22. Then,the solvent 7 such as toluene or hexane is added (solvent additionprocess). After that, the source material 6 is added via the opening ofthe container 2 (source material addition process).

Next, the temperature adjusting mechanism 3 is activated and thetemperatures of the source material 6 and the solvent 7 are adjusted tothose within a range of 15 to 25° C. This way, the rubber sourcematerial 6 is hardly dissolved in the solvent 7, thus preventingreduction of the maximum diameter and the maximum flattened-dimension ofeach block 61, before the blocks 61 are separated.

After that, the second stirring blade 53 of the lower stirring mechanism5 and the ascending stirring blade 521 of the ascending stirringmechanism 52 are rotated at a stirring speed within a range of 100 to150 rpm, and the first stirring blade 43 is rotated at a stirring speedwithin a range of 9 to 11 rpm in the same rotating direction as thesecond stirring blade 53 and the ascending stirring blade 521. Thestirring speed of the second stirring blade 53 and the ascendingstirring blade 521 are gradually increased so as to avoid a situationwhere the rubber source material 6 locking the first stirring drivedevice 41 and the second stirring drive device 51, thus leading to anexcessive load to the motor or the like of the first stirring drivedevice 41. When the stirring speed of the second stirring blade 53 andthe ascending stirring blade 521 is 1000 rpm, the rotation of the firststirring blade 43 is stopped, and resumed at a stirring speed within arange of 9 to 11 rpm, in the opposite direction to the rotationdirection of the second stirring blade 53.

While the first stirring blade 43 and the second stirring blade 53 arerotated, the blocks 61 will not be destroyed even if they are capturedin the gap between the first stirring blade 43 and the second stirringblade 53. This is because the minimum gap between these blades 43 and 53is greater than the average maximum flattened-dimension of the blocks 61but smaller than the average maximum diameter of the blocks 61, as shownin FIG. 2. As shown in FIGS. 4( a) to (c), the shear force acting on theadhesion surfaces 61 a of an block 61 and that of another block 61 movesthese blocks 61 in different directions, respectively, thus separatingthe adhesion surfaces 61 a of the blocks 61 from each other, the blocks61 being adhered to each other at their respective the adhesion surfaces61 a serving as the boarder lines. This way, each of the blocks 61 isseparated from one another while preventing destruction of the molecularstructure of the rubber (Separation process).

After the above-described stirring operation is continued forapproximately one hour, and when the blocks 61 float individually in thesolvent 7, the temperature of the blocks 61 and the solvent 7 isadjusted to 30 to 55° C., so as to facilitate dissolving of the rubberin the solvent 7, as shown in FIG. 1. Then, the second stirring blade 53and the ascending stirring blade 521 are rotated at a stirring speedwithin a range of 300 to 500 rpm and the first stirring blade 43 isrotated at a stirring speed within a range of 9 to 36 rpm, thusgenerating a flow of the blocks 61. At this time, sedimentation of theblocks 61 is prevented and the flowability of each block 61 is improved,if repeating rotation of the first stirring blade 43 and the ascendingstirring blade 521 for 10 minutes at a stirring speed within a range of300 to 500 rpm, and then within a range of 600 to 3400 rpm for 5 to 60seconds.

Continuation of the above-described stirring operation for 24 to 48hours will dissolve the blocks 61. In other words, as the result ofcontinuing the stirring of the blocks 61 with the solvent 7, each block61 starts to dissolve into the solvent 7 starting from its surface,while preserving the molecular structure of the rubber. Thus, the rubberis dissolved into the solvent 7. Through the above is produced ahigh-quality rubber solution which preserves the molecular structure ofthe rubber (dissolving process). After that, an additive or the like isadded and further stirred with the rubber solution to form a desirablerubber solution (mixing process).

The example of the present invention described above solely serves as aspecific example of the present invention, and shall not impose anylimitation to the present invention. The specific structure or the likemay be suitably modified. Further, the action and effects described inthe embodiment are no more than examples of the most preferable actionand effect brought about by the present invention, and the action andeffects of the present invention are not limited to those described inthe embodiment.

(Alternative Form)

For example, as shown in FIG. 5, the rubber solution production device 1may be structured so that the second blade 531 has an end face member533 at its leading end portion and a projection 534 at its centerportion; and that the upper stirring mechanism 4 has ahorizontally-installed member 433 disposed to face the end face member533 and the projection 534. The end face member 533, the projection 534,and the horizontally-installed member 433 form a minimum gap which isgreater than the average maximum flattened-dimension of the blocks 61but smaller than the average maximum diameter of the blocks 61. Thisincreases the number of minimum gaps in the stirring mechanism. Theabove structure provides an increased number of chances of separatingthe blocks 61, in each rotation of the stirring mechanism. Therefore,separation of the blocks 61 from one another is completed in a shorttime.

Further, the rubber solution production device 1 of the presentembodiment has the upper stirring mechanism 4 and the lower stirringmechanism 5 separately on the upper side and the lower side of thecontainer 2, respectively. However, the present invention is not limitedto this. The stirring mechanism may be disposed on one of the upper andlower sides of the container 2. Further, it is possible to provide thestirring mechanism on the upper side of the container 2, and provide anextraction valve at the bottom part of the container 2. This way, therubber solution can be extracted utilizing the weight of the rubbersolution itself. Therefore, extraction efficiency (yield) is improved.Specifically, while the yield is approximately 80% when pumping out thesolution from the upper portion of the container, the yield isapproximately 97% when extracted utilizing the weight of the solutionitself.

Further, the rubber solution production method of the present embodimentmay be adapted so that stirring is carried out under a pressureexceeding the atmospheric pressure, as shown in FIG. 6. This allowsstirring of the solvent and the rubber in an environment where thetemperature is higher than the boiling temperature of the solvent underthe atmospheric pressure. Therefore, the swelling speed of the solventrelative to the rubber is increased, and the mixability is improved by adecrease in the visibly-confirmable viscosity of the solution (theviscosity of the rubber solution). As the result, the time taken fordissolving is reduced.

The reduction of time taken for dissolving is confirmed by the followingtest. Specifically, 1.1 kg of rubber with a high-molecular mass of0.0096 kg (8.0 wt %) was stirred in toluene in the rubber solutionproduction device shown in FIG. 2, under the following productionconditions. Namely, the volume of container 2 (tank volume) was 2 L. Thepressure inside the container 2 was 0.2 MPa. The solvent temperature was125° C. (Storing body jacket 31: vapor of 160° C.). The type of solventwas toluene (boiling temperature=110.6° C.). The stirring speed was 80rpm (Anchor blade). As the result, a state in which swelling hasprogressed was observed after one hour from the beginning of stirring.Based on the state of swelling after 6 hours, it is estimated thatdissolving of the rubber could be completed in approximately 12 hours.

Measuring the rubber molecular mass of the rubber solution producedunder the pressurized environment, the rubber molecular mass was foundto be lower than that of the rubber solution produced withoutpressurization. To confirm the influence of the temperature to thisphenomenon, the rubber was rolled flat by a pressing machine, and evenlyheated (120° C., 180° C.×3 minutes). Then, the molecular mass of theheated rubber was measured. It is found out as the result that themolecular mass of the heated rubber was not lowered. From this finding,the decrease in the rubber molecular mass of the rubber solutionproduced under the pressurized environment is believed to be attributedto a factor other than the temperature; e.g., heating of the solvent andother factors.

Production of the rubber solution under the above-described pressurizedenvironment is possible by providing, to the rubber solution productiondevice 1 of the present embodiment, a pressurizing device for increasingthe pressure inside the container 2 to a pressure exceeding theatmospheric pressure, the container 2 being for airtightly storing thesource material and the solvent. The pressurizing device may be, forexample, a steel bottle for jetting an inert gas such as nitrogen orcarbon dioxide.

The pressure resistance of the container 2 is preferably 30 MPa or more.This is because of the following reason. If the solvent is to be heatedup to 200° C., as in the usual cases, a pressure-resistance ofapproximately 1 MPa should be sufficient. However, if the carbon dioxidein the container 2 is to be brought to the super critical state, thepressure for pressurization will be approximately 30 MPa at the most.Further, to ensure the airtightness of the container 2, it is preferableto use mechanical seal for the joint portion of the container 2 and theupper stirring mechanism 4 or the like, when the pressurizing pressureis approximately 1 MPa. When the pressurizing pressure exceeds 1 MPa, amagnet type seal is preferred.

REFERENCE NUMERALS

-   1 Rubber solution production device-   2 Container-   21 Cover-   22 Storing body-   3 Temperature adjusting mechanism-   4 Upper stirring mechanism-   41 First stirring drive device-   42 Second stirring shaft-   43 First stirring blade-   5 Lower stirring mechanism-   51 Second stirring drive device-   52 Ascending stirring mechanism-   521 Ascending stirring blade-   53 Second stirring blade-   54 Ascending stirring shaft-   55 Second stirring shaft-   6 Source material-   61 Block-   61 a Adhesion surface-   7 Solvent

1. A rubber solution production method, comprising the steps of: mixinga solvent into a source material including a plurality of rubber blockseach maintaining a block-state by a predetermined holding force, theblocks being adhered to one another by an adhesion force smaller thanthe holding force; and stirring the source material while applyingthereto a shear force which is greater than the adhesion force butsmaller than the holding force so as to separate the source materialinto block units, and dissolving the blocks into the solvent to producea rubber solution.
 2. The method according to claim 1, wherein thesource material is stirred while applying thereto the shear force, bymoving a plurality of stirring blades at speeds relatively differentfrom each other, the blades being disposed so that a minimum gap betweenthe blades is greater than the average maximum flattened-dimension ofthe blocks and smaller than the average maximum diameter of the blocks.3. The method according to claim 2, wherein the source material isseparated into block units by stirring the source material and thesolvent, while cooling down the same.
 4. The method according to claim3, wherein the source material and the solvent are stirred in such amanner as to add an ascending force.
 5. The method according to claim 4,wherein a stirring state is changed according to a ratio of the rubberdissolved into the solvent.
 6. The method according to claim 5, whereinthe stirring is carried out under a pressure exceeding an atmosphericpressure.
 7. The method according to claim 1, wherein the sourcematerial is separated into block units by stirring the source materialand the solvent, while cooling down the same.
 8. The method according toclaim 1, wherein the source material and the solvent are stirred in sucha manner as to add an ascending force.
 9. The method according to claim1, wherein a stirring state is changed according to a ratio of therubber dissolved into the solvent.
 10. The method according to claim 1,wherein the stirring is carried out under a pressure exceeding anatmospheric pressure.
 11. A rubber solution production device,comprising: a container configured to store a solvent and a sourcematerial including a plurality of rubber blocks each maintaining ablock-state by a predetermined holding force, the blocks being adheredto one another by an adhesion force smaller than the holding force; anda stirring mechanism configured to stir the source material and thesolvent, while applying, to the source material a shear force greaterthan the adhesion force but smaller than the holding force.
 12. Thedevice according to claim 11, wherein the stirring mechanism includes: aplurality of stirring blades disposed so that a minimum gap between theblades is greater than the average maximum flattened-dimension of theblocks and smaller than the average maximum diameter of the blocks; anda drive mechanism configured to move the stirring blades at speedsrelatively different from each other.
 13. The device according to claim12, further comprising a temperature adjusting mechanism for coolingdown the source material and the solvent.
 14. The device according toclaim 13, wherein the stirring mechanism includes an ascending stirringblade configured to add an ascending force to the source material. 15.The device according to claim 14, wherein the container is formed so asto airtightly store the source material and the solvent; and the rubbersolution production device further comprises a pressurizing device forpressurizing the inside of the container to a pressure exceeding anatmospheric pressure.
 16. The device according to claim 11, furthercomprising a temperature adjusting mechanism for cooling down the sourcematerial and the solvent.
 17. The device according to claim 11, whereinthe stirring mechanism includes an ascending stirring blade configuredto add an ascending force to the source material.
 18. The deviceaccording to claim 11, wherein the container is formed so as toairtightly store the source material and the solvent; and the rubbersolution production device further comprises a pressurizing device forpressurizing the inside of the container to a pressure exceeding anatmospheric pressure.